2-Pyridyl ketone oximes in iron(III) carboxylate chemistry: Synthesis, structural and physical studies of tetranuclear clusters containing the [Fe4(μ3-O)2]8+ ‘butterfly’ core

The use of 2-pyridyl ketone oximes, pyC(R)NOH (R = H, Me), in iron(III) carboxylate chemistry yielded the tetranuclear complexes [Fe4O2Cl2(O2CPh)2{pyC(R)NO}4] (R = H, 1; R = Me, 2). The crystal structure of 2 revealed the presence of a central [Fe4(μ3-O)2]8+ core comprising four FeIII ions in a ‘butterfly’ disposition and two μ3-O2− ions, each bridging three FeIII ions forming the ‘wings’ of the ‘butterfly’. The Mössbauer spectra from polycrystalline samples of 2 consist of composite quadrupole-split doublets, with parameters typical for high-spin iron(III) in octahedral environments. Magnetic susceptibility measurements on 2 revealed antiferromagnetic interactions between the S = 5/2 ferric ions; fits to the data required the use of two different parameters for the wingtip–body interactions. The best-fit values for these interactions were J1 = −85 cm−1 and J2 = −27 cm−1 (-2JijSiSj Hamiltonian formalism) resulting to a diamagnetic ground state.

The use of pyC(R)NOH (R = H, Me) in iron(III) benzoate chemistry yielded tetranuclear complexes presenting the [Fe4(μ3-O)2]8+ ‘butterfly’ core; the structural, spectroscopic (IR, Mössbauer) and magnetic studies of [Fe4O2Cl2(O2CPh)2{pyC(Me)NO}4] are reported.Figure optionsDownload as PowerPoint slide